Electrical heating unit



y 26, 1932- E. L. WIEGAND 1,868,620

ELECTRICAL HEATING UNI T Filed Aug. 6, 1928 gnwwiox rmeuul zaisaz.

UNITED STATES mm L. WIEGAHD, OF PIT'I'BBUBGH, PENNSYLVANIA mac-mien. name mmr Application flied Augult 0.1m. mm 10. 201,012.

This invention relates nerally to electrical heating elements, an more particularly to certain improvements upon the heating elements disclosed in my Patents Nos. 1536514330 and 1,614,331, dated January 11,

The object of the present invention is to simplify and improve the structures disclosed in t ose a tents, and at the same time preserve an maintain all their advantageous features of operation.

For some types of work a wholly sheathed element is notabsolutel necessary. This applies to applications w ere the unit 1 s properly protected when mounted in certain types of appliances such as percolators, waflle irons and other devices where the exposed refrac to is not too likely to become polluted.

his type of unit is used in connection wlth vessels made of aluminum since this metal has a high reflection factor and unless rfect contact 1s made the heat is best absor ed by radiation and the refractory material is naturally not damaged by the elevated temperature which would develop on the contact side of the element on aluminum vessels.

The easily ab'ricated, 'and in some instances is more efiicient, due to the fact that fewer parts are employed and the direct radiation of heat therefore expedited.

With these ob'ects in view, and certain others which will come apparent as the description proceeds, my invention consists in providing a one-piece sheet metal sheath in ification Fig. 1 1s a top plan view of a heatresent invention is cheaper, more which is arranged the resistor properly em-- ing element constructed in accordance with my present invention; Fig. 2 is a bottom plan view of the same; Fig. 3 is a transverse sectional view and Figs. 4, 5 and 6 are views showing different shapes of heating elements all embodying the details of my present invention.

In all forms of the present invention a sinuous resistor 1 is enveloped within a mass of suitable electrical insulating heat conducting material 2. The resistor preferably consists of a flat ribbon wire of suitable metal, shown as bent back and forth across the element in comparatively close bends, with its edges presented to the broad faces of the element. It will be understood, however, that a resistorwire of the usual form can be employed instead of the ribbon form. The mass 2 maybe of any suitable refractory insulating material, and I have found magnesium or 7 aluminum oxide or zirconium silicate, either individually where possible, or a compound of them together when desirable, with a suitable bin material such as clay, to give the necessary p during fabrication and 7: to effect homogeneity in the final product.

The mass 2 of refractory material which surrounds and envelopes the resistor is highly compacted within a sheet metal sheath or casing 3, this sheet metal sheath or casin being constructed of very thin sheet metai and comprising a bottom portion 3 and side portions 3", the side portions being comparatively shallow or narrow as com ared with the width of the bottom portion. 's sheath or casing can therefore be described as a onepiece sheet metal sheath, channel shaped in cross section.

The resistor, it will be noted, is arranged within the sheet metal sheath but is spaced therefrom, and the refractory material 2 which envelopes the resistor completely fills the sheathand therefore properly spaces the resistor within the sheath.

The refractory material is highly com pacted within the sheath and the edges 3 of the sides 3" of the sheath are rolled or turned over the adjacent portions of the refractory material, that is to say the edges of the sides of the sheath are rolled or turned toward each other thereby overlapping the edges of the refractory and serving to maintain the refractory material .within the sheath.

The ends of theresistor 1 are connected to 5 terminals 10 which have thei'renlarged inner ends or bases towhich the resistor is attached embedded within the mass 2 of refractory material. Theterminals extend outwardly throughholeal ll produced in the bottom. of; 10 the sheath, the holes being of sufficient size:

to; insure proper. spacing and consequential insulation and, as illustrated, the hole is closed by a washer 12 of mica or other suitable insulating material that fits over the terminal and is engaged against the outer side of the bottom of the sheath.

In addition to compacting the refractory material and turning over the ed esof the sheath, thismaterial is dried and ba ed either by an external source of heat orby energizing the resistor. As a result of this baking, the refractory is. converted into a homogeneous hard filling, and due to the fact that the outer surface thereof is made flush with the rolled over edges of the sheath, these rolled over edges serve to securely maintain the refractory firmly within the sheath. In other words, the sheath, refractory, and resistor enveloped therein, are rigidly andintimately united into a composite product.

In Figs. 1, 2 and 3 I have shown the heating element substantially in the form of a ring, while in Fig. 4 it is shown in the form of a circular heating element having a small central circular opening. In Fig. 5 I have shown it as triangular in form, and in Fig. 6 I have shown it as V-shaped. In my patents previously referred to, such shapes were also employed, and furthermore the heating ele- 40 ment disclosed in said patents were in'some instances, curved or dished to conform to certain shapes of articles to be heated, and in my present invention the heating element can also be so bent or shaped if desired, this bendprior-to the drying and baking of the refractor material.

' 1 x 1 order to more securely bind the refractory and sheath together, a suitable coating of glazin may be arranged upon the refractory and aked at the same time that the refractory is baked. i

My present type of heating element possesses certain advantages over any heating elements heretofore constructed, inasmuch as I only employ the sheath, resistor and filling of refractory material, thus dispensing with a separate covering plate or strip. This not only avoids the use of this amount of metal, but it brings about a more rapid radiation of heat as this covering member heretofore-employed necessarily absorbed a definite quantity of heat units.

urthermore, a perfectly smooth heating unit can be provided inasmuch as the refrac-- ing or shaping process of course taking place imam It will also be,understood that the sheath can have its bottom portion either perforate oryimperforate and still accomplish all of the proper functions of the sheath or casing. .urthermore, by dispensing with the se arate cover, a more uniform product can e obtained by rolling the edges of the sheath over the adjacent portions of the refractory and these rolled-over edges impart to the sheath a definite amount of rigidity, particularly when the ring or circular type of heating element is produced.

It will thus be seen that I. provide a simplified electrical heating element consistin of fewer parts and one which is superior to t ose hereto ore produced insofar as the rapid and direct radiation of heat is concerned.

Having thus described my invention, what I claim is:

1. An electrical heating unit of the character described comprising a one piece sheet metal sheath substantially channel shaped in cross section, a resistor arranged within said sheath, a homogeneous compact mass of refractory insulating material completely en- Veloping the resistor and filling the said sheath except for the space occupied by said resistor, the opposite edges of said sheathbeing bent over toward each other and overlapping the adjacent edges of the refractory material and embedded therein so that the refractory material is flush with the turnedover edges of the sheath, and terminals connected with said resistor and emerging from said sheath and adapted for connection with a source of current.

2. In an electrical heating unit of the character described, comprising a one-piece sheet metal sheath substantially channel shaped in cross section and having its entire peripheral edge bent upwardly to form an open face casing, a resistor arranged within said casing,

a homogeneous compacted mass of refractory insulating material filling said casing except for the space occupied by said resistor, and resistor being supported solely by said refractory insulating material, the opposite edges I of said casing being bent over toward each other and overlapping the adjacent edges of the refractor in so that-t erefractory material is flush materialand embedded therewith said overturned edges, and terminals.

connected with said resistor and emerging from said sheath and adapted for connection.

with a source of current.

3. In an electrical heating unit of the character described, comprising an endless sheet 1 metal sheath substantially channel shaped in cross section and havin its entire peripheral edge bent upwardly to orm an open face 088- ing, a resistor arranged within said casing, a

homogeneous compacted mass of refractory insulating material filling said casing except 'for the space occupied by said resistor, said resistor being supported solely by said refractory insulating material, the opposite edges 7 of said casing being bent overtoward each other and overlapping the adjacent edges of the refractory material and embedded therein so that the refractory material is flush with said overturned edges, and terminals connected with said resistor and emerging from said sheath and adapted for connection with a source of current. 4. An electrical resistance heating unit of the character describedhaving an exposed refractory face and comprising a sheath substantially channel-sha ed in cross-section, a resistor arranged withln said sheath, a homogeneous compacted mass of refractory insulating material enveloping said resistor, the opposite edges of said sheath being bent over toward each other and overlapping the adjacent edges of the refractory material and disposed substantially flush with the exposed v face of the unit and terminals emerging from 25 said sheath and adapted for connection with a source of current.

5. An electrical resistance heating unit of the character described having an exposed refractory face and comprising a sheath sub- 30 .stantially channel-shaped in cross section, a resistor arranged within said sheath, a mass of refractory insulating material enveloping said resistor, the opposite sides of said sheath having inwardly directed portions, the refractory insulating material interlockin with said inwardl directed portions an having its surface dlsposed substantially flush with the edges of said sheath.

6. In an electrical resistance heating unit of the character described having an exposed molded refractory face and comprising a sheath, a resistor arranged within said sheath, a mass of refractory insulating material enveloping said resistor, the opposite 45 sides of said sheath having inwardly directed portions, the refractory nsulating material interlocking with said inwardly directed portions and having its surface disposed substantially flush with the edges of said sheath.

7 In testimony whereof I hereunto afiix my signature.

EDWIN L. WIEGAND. 

